JP2003048408A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of preventing cracks generated in a bottom of a small groove for suppressing partial wear when the tire rides over a curb or the like. SOLUTION: A plurality of projections 26 are formed on a groove wall 24A on the outside in the tire width direction of a defense groove 24 provided on a shoulder rib 22 with intervals in the tire circumferential direction. When the tire rides over a projection 30 such as the curb, the defense groove rib 22A may be opened. However, the projection 30 such as the curb hits the projections 26, the contact area between the bottom of the defense groove 24 and the projection 30 such as the curb is reduced or becomes zero, and generation of cracks from the bottom of the defense groove 24 is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire suitable for heavy-duty vehicles such as trucks and buses, in which uneven wear of ribs is suppressed.

[0002]

2. Description of the Related Art As pneumatic tires used in heavy-duty vehicles such as trucks and buses, various pneumatic tires having a plurality of circumferentially extending ribs on a tread have been proposed.

A pneumatic tire having ribs extending in the circumferential direction has various problems such as uneven wear of the ribs and rib tear due to running on a bad road, and various measures have been taken.

As one of the countermeasures, as shown in FIG. 5A, a shoulder side rib 100 called shoulder edge wear, which is apt to cause uneven wear, extends in a circumferential direction called a defense groove (DG) 102. There is a technique in which a fine groove is provided to prevent uneven wear on the inside of the defense groove 102 in the tire width direction.

[0005]

However, in the above technique, in-section tensile strain in the groove bottom of the defense groove 102, circumferential shear strain, and as shown in FIG. Since the corners of 104 contact each other, there is a problem that cracks occur at the groove bottom of the defense groove 102.

In consideration of the above facts, the present invention provides a pneumatic method capable of preventing cracks (tears) from being generated in the groove bottoms of the fine grooves for suppressing uneven wear even when riding on a curb or the like. The purpose is to provide tires.

[0007]

According to a first aspect of the present invention, there is provided a pneumatic tire having a tread having a plurality of ribs divided by a plurality of main grooves extending in the circumferential direction, the tire width direction The outermost rib is formed with a narrow groove that extends along the tire circumferential direction and has a narrower groove width than the main groove, and a plurality of groove walls of the narrow groove are arranged at intervals in the tire circumferential direction. It is characterized in that the projections of are formed.

Next, the operation of the pneumatic tire according to claim 1 will be described.

When a lateral force acts on the pneumatic tire, the fine groove appropriately reduces the ground contact pressure applied to the outermost rib in the tire width direction (hereinafter, appropriately referred to as a shoulder rib), so that the ground contact pressure distribution of the shoulder rib is reduced. By making the
It suppresses the occurrence of local wear, which is a core of uneven wear, and suppresses the generated local wear from growing and growing inward of the shoulder ribs in the tire axial direction (on the tire equatorial plane side).

Further, while running, there is a case in which the shoulder area rides on a curb and the like and the outer portion of the narrow groove of the shoulder rib opens, but the contact area between the groove bottom of the narrow groove and the curb is reduced (or zero). It is possible to suppress the occurrence of cracks from the groove bottom of the narrow groove.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the dimension from the tread surface ground contact end of the tread to the narrow groove is 1 mm or more and less than 30 mm.

Next, the operation of the pneumatic tire according to claim 2 will be described.

If the dimension from the tread surface grounding end of the tread to the narrow groove is 30 mm or more, the uneven wear property of the shoulder rib is deteriorated.

If the dimension from the tread surface grounding end of the tread to the narrow groove is less than 1 mm, the shoulder rib entering the grounding surface is too small and the uneven wear property of the shoulder rib deteriorates.

Therefore, it is preferable to set the dimension from the tread surface grounding end of the tread to the narrow groove to 1 mm or more and less than 30 mm.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the protrusions extend continuously from the tread surface toward the groove bottom.

Next, the operation of the pneumatic tire of claim 3 will be described.

By forming the protrusions so as to extend continuously from the tread surface toward the groove bottom, it is possible to prevent catching when the curb climbs up.

The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein:
The dimension of the protrusion in the tire width direction is 0.5 mm or more and 5 mm or less.

Next, the operation of the pneumatic tire according to claim 4 will be described.

When the dimension of the protrusion in the tire width direction is less than 0.5 mm, it is impossible to prevent the curb from contacting the groove bottom of the narrow groove.

On the other hand, the dimension of the protrusion in the tire width direction is 5 mm.
If it exceeds, the resistance in the narrow groove increases and the water flow deteriorates.

Therefore, it is preferable to set the dimension of the protrusion in the tire width direction to 0.5 mm or more and 5 mm or less.

The invention according to claim 5 is the pneumatic tire according to any one of claims 1 to 4, wherein:
The dimension of the protrusion in the tire circumferential direction is characterized in that it is not less than the tire width direction dimension of the protrusion and not more than 30 mm.

Next, the operation of the pneumatic tire according to claim 5 will be described.

When the dimension of the protrusion in the tire circumferential direction is smaller than the dimension of the protrusion in the tire width direction, the rigidity of the protrusion is excessively reduced, and the contact area between the groove bottom of the fine groove and the curb cannot be reduced.

On the other hand, the dimension of the protrusion in the tire circumferential direction is 30 mm.
If it exceeds, the uneven wear property deteriorates.

Therefore, it is preferable to set the dimension of the protrusion in the tire circumferential direction to be not less than the dimension of the protrusion in the tire width direction and not more than 30 mm.

The invention according to claim 6 is the pneumatic tire according to any one of claims 1 to 5, wherein:
It is characterized in that the interval between two protrusions adjacent to each other in the circumferential direction is not less than the dimension of the protrusion in the tire circumferential direction and not more than 50 mm.

Next, the operation of the pneumatic tire according to claim 6 will be described.

If the distance between two protrusions adjacent in the circumferential direction is less than the dimension of the protrusions in the tire circumferential direction, the volume of the groove becomes small and the drainage performance deteriorates.

The distance between two protrusions adjacent in the circumferential direction is 50.
When it exceeds mm, the gap between the protrusions becomes too wide, and the curbstone or the like easily contacts the groove bottom between the protrusions.

Therefore, it is preferable to set the interval between two protrusions adjacent to each other in the circumferential direction to be not less than the dimension of the protrusion in the tire circumferential direction and not more than 50 mm.

The invention according to claim 7 is the pneumatic tire according to any one of claims 1 to 6, wherein:
The groove bottom cross section of the narrow groove has a substantially arc shape, and a gap is provided between the groove bottom side end of the protrusion and the groove bottom deepest part of the narrow groove.

Next, the operation of the pneumatic tire according to claim 7 will be described.

By making the groove bottom cross section of the narrow groove substantially arc-shaped, it is possible to prevent stress concentration near the groove bottom and to suppress the occurrence of cracks from the groove bottom.

If a gap is not provided between the groove bottom side end of the protrusion and the groove bottom deepest part of the narrow groove, the groove bottom cross section of the narrow groove cannot be formed into a substantially arc shape. The radius of curvature of the groove bottom becomes too small, and the groove bottom is repeatedly strained when the tire rolls, and the crack resistance deteriorates.

The invention according to claim 8 is the pneumatic tire according to any one of claims 1 to 7, wherein:
The protrusion is formed on a groove wall of the narrow groove on the tire equatorial plane side.

Next, the operation of the pneumatic tire according to claim 8 will be described.

In the pneumatic tire of the eighth aspect, the protrusion formed on the groove wall of the narrow groove on the tire equatorial plane side reduces the contact area between the groove bottom and the curb.

The invention according to claim 9 is the pneumatic tire according to any one of claims 1 to 8.
The protrusion is formed on a groove wall on the shoulder side of the narrow groove.

Next, the operation of the pneumatic tire according to claim 9 will be described.

In the pneumatic tire according to the ninth aspect, the protrusion formed on the groove wall on the shoulder side of the narrow groove reduces the contact area between the groove bottom and the curb.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the pneumatic tire of the present invention will be described with reference to FIGS.

As shown in FIG. 2, the pneumatic tire 10 of the present embodiment (tire size: 315 / 80R22.5)
Tread 12 (tread width W) has tire equatorial plane C
Tire axial direction across L (arrow L direction and arrow R direction)
A circumferential main groove 14 formed on both sides and extending linearly along the tire circumferential direction, and a circumferential main groove 16 formed outside the circumferential main groove 14 in the tire axial direction and extending linearly along the tire circumferential direction. Depending on the center rib 18 and the second rib 2
0 and shoulder ribs 22 are defined.

The shoulder rib 22 is formed with a defense groove 24 extending linearly along the circumferential direction toward the shoulder and narrower than the circumferential main groove 16.

A portion of the shoulder rib 22 closer to the shoulder than the defense groove 24 is referred to as a defense groove 22A.

As shown in FIG. 1, the cross-sectional shape of the groove bottom of the defense groove 24 is formed in a semicircular shape in order to prevent stress concentration that causes cracks. Of course, it is preferable that the radius of curvature of the groove bottom is as large as possible within the range of the groove width.

Here, the tread 12 ground contact end 12 of the tread 12
The dimension a from A to the defense groove 24 is preferably 1 mm or more and less than 30 mm.

The tread surface grounding end 12A here is the pneumatic tire 10 according to JATMA YEAR BOOK (2
Installed on the standard rim specified by the Japan Automobile Tire Manufacturers Association Standard (2001 version), JATMA YEAR BO
The maximum load capacity (maximum load capacity) of a single wheel filled with 100% of the internal pressure (maximum air pressure) corresponding to the maximum load capacity (internal pressure-load capacity in bold in the load capacity correspondence table) in applicable sizes and ply ratings for OK It is the ground contact end in the tire width direction when is applied.

At the place of use or production site, TRA
When the standards and ETRTO standards are applied, follow each standard.

The groove width w of the defense groove 24 is
In the pneumatic tire 10 having a tire size of 315 / 80R22.5, 2.0 to 3.0 mm is preferable so that a sudden step difference in ground contact pressure does not occur in the shoulder rib 22.

Further, the depth D of the defense groove 24
₁ is 60% to 10% of the depth D ₀ of the adjacent circumferential main groove 16
The range of 0% is preferable.

A plurality of protrusions 26 are formed on the groove wall 24A on the outer side in the tire width direction of the defense groove 24 at intervals in the tire circumferential direction.

The dimension c of the protrusion 26 in the tire width direction is 0.
It is preferably 5 mm or more and 5 mm or less.

The dimension e of the protrusion 26 in the tire circumferential direction is preferably not less than the dimension c of the protrusion 26 in the tire width direction and not more than 30 mm.

The distance b between the protrusions 26 is preferably not less than the dimension e of the protrusions 26 in the tire circumferential direction and not more than 50 mm. It

The projection 26 continuously extends linearly from the tread surface to the groove bottom, but terminates before the groove bottom (semicircular arc portion).

It is preferable that the end of the projection 26 on the groove bottom side is brought close to the groove bottom side to a position where it does not reach the groove bottom (semi-circular arc portion).

In this embodiment, the tread width W is 250 m.
m, the groove width of the circumferential main groove 14 is 10.6 mm, the circumferential main groove 1
6 has a groove width of 15.4 mm and the center rib 18 has a width of 31.
8 mm, the width of the second rib 20 is 31.7 mm, and the width of the shoulder rib 22 is 31.9 mm.

The defense groove 24 has a groove width w of 2.5 mm, a depth D ₁ of 11.5 mm, a radius of curvature r of the groove bottom of 1.25 mm, and a dimension a from the tread surface grounding end 12A to the defense groove 24. It is 17 mm.

The projection 26 has a space dimension b of 20 mm,
Dimension c is 1.25mm, groove bottom end to groove bottom (deepest part)
Has a dimension d of 1.5 mm and a dimension e of 2.0 mm.

(Operation) Next, the operation of the pneumatic tire 10 of this embodiment will be described.

When a lateral force acts on the pneumatic tire 10,
By appropriately reducing the ground contact pressure applied to the shoulder ribs 22 by the defense groove 24 and making the ground contact pressure distribution of the shoulder ribs 22 more uniform, it is possible to suppress the occurrence of local wear, which is the core of uneven wear, and to generate it. The local wear is suppressed from growing and growing inward in the tire axial direction of the shoulder rib 22 (on the tire equatorial plane CL side).

While the vehicle may run on a protrusion 30 such as a curb during driving and the defense groove 22A may open as shown in FIG. 3, the cross-sectional shape of the groove bottom of the defense groove 24 is a semicircle. The shape prevents stress concentration, and the projection 30 such as a curb hits the projection 26 continuously extending from the tread surface toward the groove bottom, and the groove bottom of the defense groove 24 and the projection 30 such as a curb contact. Since the area can be reduced or reduced to zero, the generation of cracks from the groove bottom can be effectively suppressed.

In addition, from the grounding end to the defense groove 2
If the dimension a up to 4 is less than 1 mm or more than 30 mm,
The uneven wear property of the shoulder rib 22 is deteriorated.

The dimension c of the protrusion 26 in the tire width direction is 0.
If it is less than 5 mm, the contact area between the groove bottom of the defense groove 24 and the protrusion 30 such as a curb cannot be reduced, and if the dimension c exceeds 5 mm, the resistance in the defense groove 24 becomes large and the water flow deteriorates. To do.

When the dimension e of the protrusion 26 in the tire circumferential direction becomes smaller than the dimension c of the protrusion 26 in the tire width direction, the protrusion 2
Since the rigidity of No. 6 is too low, the contact area between the groove bottom of the defense groove 24 and the protrusion 30 such as a curb cannot be reduced, and when the dimension e exceeds 30 mm, the uneven wear property deteriorates.

The distance b between the protrusions 26 is the protrusion 2
If it is less than the dimension e in the tire circumferential direction of 6, the groove volume becomes small and the drainage property deteriorates.

When the distance b exceeds 50 mm, the protrusion 26
The gap between the protrusion 26 and the protrusion 26 becomes too wide, and the protrusion 30 such as a curb easily contacts the groove bottom between the protrusions 26.

In the above embodiment, the projection 26 is formed on the groove wall 24A on the outer side in the tire width direction of the defense groove 24.
However, the present invention is not limited to this, and the same action and effect can be obtained by forming the groove wall on the opposite side (tire equatorial plane CL side) as shown in FIG. (Test Example) In order to confirm the effect of the present invention, a tire of a conventional example and a tire of an example to which the present invention was applied were prepared and compared with respect to tearing property and uneven wear property.

Tire of Example: The pneumatic tire (FIGS. 1 to 3) described in the embodiment.

Conventional tire: A tire in which no projection is provided on the groove wall of the defense groove.

All the tires used in the test had a tire size of 315 / 80R22.5 and a rim size of 9.0.
It was mounted on a 0 × 22.5 rim and filled with an internal pressure of 825 kPa.

Tear test: A vehicle equipped with a test tire was run for 10,000 km and then the curb (height 1
(5 cm) was repeatedly climbed up and down 5 times, and the depth of the crack generated at the groove bottom of the defense groove was measured. The evaluation is represented by an index with the crack length of the conventional example as 100, and the smaller the value, the shallower the crack depth and the better the performance.

Uneven wear test: A vehicle equipped with a test tire was run for 100,000 km, and the amount of wear of a rib located on the tire equatorial side of the defense groove was measured. The evaluation is represented by an index with the wear amount of the conventional example being 100, and the smaller the value, the less uneven wear and the better performance.

[0077]

[Table 1] From the test results, it can be seen that the tires of Examples 1 to 5 were able to improve the tearability without reducing the uneven wear resistance.

[0078]

As described above, since the pneumatic tire of the present invention has the above-mentioned structure, it does not reduce uneven wear resistance and is a fine groove for suppressing uneven wear when riding on a curb or the like. It has an excellent effect that cracks (tears) generated at the bottom can be prevented.

[Brief description of drawings]

FIG. 1 is a perspective view near a shoulder of a tread of a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an outer contour of a pneumatic tire according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view in the vicinity of the shoulder of the tread showing a state in which the defense groove is opened on the curb.

FIG. 4 is a cross-sectional view near the shoulder of a tread of a conventional tire showing a state in which a defense groove is opened by riding on a curb.

FIG. 5A is a cross-sectional view of a conventional tire,
(B) is a cross-sectional view of a conventional tire mounted on a curb.

[Explanation of symbols]

10 pneumatic tires 12 treads 14 circumferential main groove 16 circumferential main groove 18 Center rib 20 second rib 22 Shoulder rib 24 Defense Groove 26 Protrusion

Claims (9)

[Claims] 1. A pneumatic tire having a tread provided with a plurality of ribs sectioned by a plurality of main grooves extending in the circumferential direction, wherein the outermost rib in the tire width direction extends along the tire circumferential direction. A narrow groove is formed that extends and has a groove width narrower than that of the main groove, and a plurality of protrusions are formed on a groove wall of the narrow groove at intervals in the tire circumferential direction, Pneumatic tires. 2. The pneumatic tire according to claim 1, wherein a dimension from the tread surface grounding end of the tread to the narrow groove is 1 mm or more and less than 30 mm. 3. The pneumatic tire according to claim 1, wherein the protrusion extends continuously from the tread surface toward the groove bottom. 4. The dimension of the protrusion in the tire width direction is 0.
It is 5 mm or more and 5 mm or less, The pneumatic tire of any one of Claim 1 thru | or 3 characterized by the above-mentioned. 5. The pneumatic tire according to claim 1, wherein a dimension of the protrusion in a tire circumferential direction is not less than a tire width direction dimension of the protrusion and not more than 30 mm. tire. 6. The distance between two protrusions adjacent in the circumferential direction is
The pneumatic tire according to any one of claims 1 to 5, wherein the protrusion has a dimension in the tire circumferential direction of not less than 50 mm. 7. The groove bottom cross section of the narrow groove has a substantially arc shape, and a gap is provided between the groove bottom side end of the protrusion and the groove bottom deepest part of the narrow groove. Claim 1
The pneumatic tire according to claim 6. 8. The pneumatic tire according to claim 1, wherein the protrusion is formed on a groove wall on the tire equatorial plane side of the narrow groove. 9. The pneumatic tire according to claim 1, wherein the protrusion is formed on a groove wall on the shoulder side of the narrow groove.